1. Field of the Invention
A method utilized in a wireless communication and related communication device are disclosed, and more particularly, to a method of handling location services in a wireless communication system and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred as user equipments (UEs).
Location service (LCS) is used for UE positioning and includes a mobile originate location request (MO-LR), a mobile terminated location request (MT-LR), and a network induced location request (NI-LR). The LCS is a service concept in system (e.g. Global System for Mobile Communications (GSM) or Universal Mobile Telecommunications System (UMTS)) standardization, and requires positioning functionality for implement. The LCS utilizes one or more positioning methods, such as cell identity (ID) based method, observed time difference of arrival (OTDOA) method, assisted Global Navigation Satellite System (A-GNSS) method, etc, in order to determine the location of the UE.
In the LTE system, the UE initiates a location service (e.g. the MO-LR) with an evolved serving mobile location centre (E-SMLC) in the LTE system when the LTE system supports the positioning functionality. The E-SMLC manages the support of different location services for the UE, including positioning of UE and delivery of assistance data to UE. On the other hand, the UE triggers a circuit switched (CS) fallback procedure to other system (e.g. the GSM or the UMTS) supporting the positioning functionality when the LTE system does not support the positioning functionality. Then, the UE initiates the MO-LR in the UMTS/GSM. That is, the CS fallback allows the UEs to switch (e.g. handover, cell change order or redirection) from the E-UTRAN to other network (e.g. Universal Terrestrial Radio Access Network (UTRAN) of the UMTS) to initiate the location service in the UMTS. The CS fallback procedure shall be well-known in the art, so it is not given herein.
Similarly, the LTE network may initiate the MT-LR/NI-LR to the UE if the LTE network supports the positioning functionality, otherwise the network initiates the MT-LR/NI-LR to the UE in the UMTS network by the CS fallback procedure.
Due to unclear specification for the location services in the LTE system, several scenarios are described as follows.
In the first scenario, for a UE with UMTS/LTE positioning and CS fallback capabilities, the UE camping on a LTE cell can either initiate the MO-LR in LTE or in UMTS by CS fallback procedure. However the network cannot control the UE to initiate the MO-LR in LTE or in UMTS, thereby causing mobility management or load problem.
In the second scenario, for a UE with UMTS/LTE positioning and CS fallback capabilities, the UE camping on a LTE cell can either initiate a MO-LR in LTE network or in UMTS network by CS fallback procedure. However, the LTE system does not provide mechanism for the UE to select LTE or UMTS network to initiate the MO-LR. The UE fails to initiate the MO-LR if the UE selects the LTE network but the LTE network does not support positioning functions. After that, the UE indicates to the user that the initiation of MO-LR location service fails. In this situation, the UE does not initiate the MO-LR in the UMTS network even the UMTS network supports positioning functions.
In the third scenario, the network does not know if the UE supports LTE positioning protocol (LPP). Therefore the network cannot determine to initiate the MT-LR/NI-LR in LTE network or UMTS network by the CS fallback procedure. Please note that, the LPP is terminated between the UE and the E-SMLC, and is a point-to-point positioning protocol between the E-SMLC the UE in order to position the UE. The LPP supports positioning and location related services for the UE accessing E-UTRAN, and is intended to enable positioning for LTE using a multiplicity of different position methods.
In the fourth scenario, the network may initiate the MT-LR/NI-LR to the UE camping on LTE network in UMTS network by CS fallback, and the UE rejects the MT-LR/NI-LR due to not supporting LCS or positioning functionality. The drawback is that the UE is unnecessarily handover to GSM or UTRAN network. This unnecessary handover to GSM/UTRAN from LTE wastes resources (i.e. power, bandwidth) because of signaling messages exchange between the UE and network and between LTE and GSM/UTRAN networks. Furthermore, the UE possibly reselects back to LTE network after the UE enters idle mode. This is an unnecessary reselection and wastes UE power and possibly misses paging during the reselection.